More than 5% of this — $1.1 billion — came in just two weeks over Christmas. Apple says it set a new record for single day App Store sales on Christmas day, which was then broken a week later, on January 1, when customers spent more than $144 million.

In a statement, Apple SVP of worldwide marketing Phil Schiller hailed the news: "The App Store had a holiday season for the record books. We are excited that our customers downloaded and enjoyed so many incredible apps for iPhone, iPad, Mac, Apple Watch and Apple TV, spending over $20 billion on the App Store last year alone ... We're grateful to all the developers who have created the most innovative and exciting apps in the world for our customers. We can't wait for what's to come in 2016."

Apple claims that it has now made nearly $40 billion for developers since the App Store's launch in 2008 — a third of it in 2015.

The Cupertino company takes 30% of sales made through the App Store, so those $20 billion sales in 2015 translate in $6 billion in revenue from the App Store.

The Wall Street Journal has pointed out that the figures, while record-breaking, appear to represent a slowdown in growth (albeit a small one). Year-on-year growth sales growth was around 40% in 2015, while it was 50% in 2014.

According to data from analytics company App Annie published in October 2015, the Google Play Store is significantly larger than Apple's App Store — it enjoys up to 90% more downloads. Despite this, however, the App Store's revenue was allegedly 80% greater than the Play Store in Q3 2015.